1. Field of the Invention
The present invention relates to a portable terminal, and more particularly, to a method for gauging a battery voltage of a portable terminal which uses batteries having different capacities.
2. Background of the Related Art
Generally, a portable terminal is designed to be detached to use a plurality of batteries in preparation for impossible recharging for a long time. Examples of batteries fixed to the portable terminal include a small capacity type, a medium capacity type and a large capacity type.
To use the batteries having different capacities in one portable terminal, exact gauging is required. For exact gauging, a device capable of gauging a battery voltage depending on each capacity is required.
However, it is actually difficult to provide a device capable of gauging remaining voltage capacity of each battery due to complexity of hardware of the portable terminal, its size and cost.
Before such a gauging of the battery, voltage values corresponding to a low voltage alarm time and power cutoff time should be gauged.
Such a gauging of the battery voltage values is to prevent error operation of hardware from occurring when the remaining voltage of the battery is less than a voltage for operating the portable terminal.
A related art apparatus and method for gauging a battery voltage of a portable terminal will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a related apparatus for gauging a battery voltage of a portable terminal, FIG. 2 is a flow chart showing a related art method for gauging a battery voltage of a portable terminal, and FIG. 3 is a diagram showing battery available time and alarm time displayed in a display unit of the portable terminal in accordance with the related art method for gauging a battery voltage of a portable terminal.
As shown in FIG. 1, the related art apparatus for gauging a battery voltage of a portable terminal includes an A/D converter 1 for converting an analog voltage level output from a cathode of a battery to a digital voltage level, a gauging unit 2 for gauging the converted digital voltage level at a constant period, a timer 3 for inputting time interval designated in the gauging unit 2, a display unit 4 for displaying remaining capacity of the battery from an output of the gauging unit 2, and a power controller 5 for controlling power of hardware depending on an output voltage of the gauging unit 2.
The operation of the related art apparatus for gauging a battery voltage of a portable terminal will be described below.
The analog voltage level output from the cathode of the battery is converted to a digital voltage level through the A/D converter 1 of a predetermined bit. At this time, the timer 3 outputs a signal to the gauging unit 2 at a prescribed time interval.
The gauging unit 2 receives the signal from the timer 3 and performs gauging by sampling the digital value converted by the A/D converter 1. At this time, the gauging unit 2 determines a range of a specific voltage level in a prescribed period and compares the prescribed period with a period corresponding to a sampling value, thereby displaying the resultant value in the display unit 4.
The related art method for gauging a battery voltage of a portable terminal will be described with reference to FIG. 2.
The digital value converted by the A/D converter is read at a prescribed constant period (S1).
The digital value read at the prescribed constant period is gauged, and it is determined whether the gauging value is greater than a prescribed reference lower limit value (S2).
As a result of the determination (S2), if the gauging value is less than the prescribed reference lower limit value, a power cutoff state is displayed in the display unit and an end routine of the terminal is performed to cut off the power (S3xcx9cS5).
Meanwhile, as a result of the determination (S2), if the gauging value is greater than the prescribed reference lower limit value, it is determined whether the gauging value is less than the prescribed reference upper limit value (S6).
Subsequently, as a result of the determination (S6), if the gauging value is less than the prescribed reference upper limit value, a low voltage alarm state and current remaining capacity of the battery are displayed in the display unit (S7xcx9cS8).
In the aforementioned related art method for gauging a battery of a portable terminal, as shown in FIG. 3, upper and lower limits of a low voltage are preset depending on the capacity of the battery. A corresponding period of the sampled is value is determined through the gauging unit 2 so that the current remaining capacity of the battery is displayed in the display unit 4.
Therefore, when the gauging value reaches a level corresponding to low voltage, the low voltage alarm state is displayed in the display unit to allow a user to recognize the remaining capacity of the battery. If the gauging value is lowered less than an allowed low voltage level, the power cutoff state is displayed in the display unit.
After the end routine of the terminal is performed, the power controller is instructed to cut off the power so that error operation of the terminal can be avoided. Thus, the power of the terminal is cut off.
However, the aforementioned related art apparatus and method for gauging a battery of a portable terminal has several problems.
If the capacity of the battery is greater than the reference capacity, variation of the voltage at the time of the power cutoff rapidly occurs. This could lead to short required time between the low voltage alarm time and the power cutoff time of the terminal. In this case, the low voltage alarm may not be exactly displayed or the power of the terminal may be cut off abnormally without the end routine.
Furthermore, if the capacity of the battery is less than the reference capacity, the low voltage alarm state may continuously be displayed or the power may be cut off in even case where the available time of the battery remains sufficiently.
Accordingly, the present invention is directed to a method for gauging a battery voltage of a portable terminal that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method for gauging a battery voltage of a portable terminal in which low voltage alarm display time and power cutoff time are determined by obtaining characteristic of a discharge curve slope of the battery, thereby improving reliability of the battery and increasing its available time.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method for gauging a battery voltage of a portable terminal according to the present invention includes the steps of converting an analog voltage value output from a battery to a digital voltage value, sampling the converted digital voltage value at a constant period, comparing the sampled digital voltage value with a predetermined number of previously sampled digital value to obtain a value of a discharge curve slope of the battery, and displaying remaining state of the battery depending on the obtained slope value.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.